Over the years, general purpose railway boxcars have progressed from relatively simple wooden structures mounted on flat cars to more elaborate arrangements including insulated walls and refrigeration equipment. Various types of insulated boxcars are presently manufactured and used. A typical insulated boxcar includes an enclosed structure mounted on a railway car underframe. The enclosed structure generally includes a floor assembly, a pair of side walls, a pair of end walls, a roof and various support posts. The side walls, end walls and roof often have an outer shell, one or more layers of insulation and interior paneling.
The American Association of Railroads (AAR) sets various design requirements for insulated and refrigerated railcars. One such requirements relates to a heat transmission value, ua. The lower the ua value, then the less refrigeration needed for a refrigerated car. Thus, it is desirable to have a low a ua as possible for an insulated or refrigerated railcar. Much of the heat loss for such a railcar is through the side posts which are typically made of steel. The steel of the side posts is a much better conductor of heat than foam insulation used in the cars, so the heat transfer through these posts is large despite their smaller cross-sectional area. Fiber reinforced plastic (FRP) is typically used in the manufacture of many insulated and refrigerated railcars, such as for interior paneling.